Support huge page in do_shmem_file_read when possible. Still have room to improve, since we re-search the page in page cache everytime, but for huge page, we might save some searches and reuse the huge page for the next read across page boundary.
Signed-off-by: Ning Qu <[email protected]> --- mm/shmem.c | 52 ++++++++++++++++++++++++++++++++++++++-------------- 1 file changed, 38 insertions(+), 14 deletions(-) diff --git a/mm/shmem.c b/mm/shmem.c index 90f2e0e..7065ae5 100644 --- a/mm/shmem.c +++ b/mm/shmem.c @@ -1765,13 +1765,25 @@ shmem_write_end(struct file *file, struct address_space *mapping, return copied; } +static unsigned long page_cache_to_mask(struct page *page) +{ + if (page && PageTransHugeCache(page)) + return HPAGE_PMD_MASK; + else + return PAGE_CACHE_MASK; +} + +static unsigned long pos_to_off(struct page *page, loff_t pos) +{ + return pos & ~page_cache_to_mask(page); +} + static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_t *desc, read_actor_t actor) { struct inode *inode = file_inode(filp); gfp_t gfp = mapping_gfp_mask(inode->i_mapping); struct address_space *mapping = inode->i_mapping; pgoff_t index; - unsigned long offset; enum sgp_type sgp = SGP_READ; /* @@ -1783,25 +1795,29 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ sgp = SGP_DIRTY; index = *ppos >> PAGE_CACHE_SHIFT; - offset = *ppos & ~PAGE_CACHE_MASK; + i_split_down_read(inode); for (;;) { struct page *page = NULL; pgoff_t end_index; unsigned long nr, ret; loff_t i_size = i_size_read(inode); + int flags = 0; +#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE + flags |= AOP_FLAG_TRANSHUGE; +#endif end_index = i_size >> PAGE_CACHE_SHIFT; if (index > end_index) break; if (index == end_index) { nr = i_size & ~PAGE_CACHE_MASK; - if (nr <= offset) + if (nr <= pos_to_off(page, *ppos)) break; } desc->error = shmem_getpage(inode, index, &page, sgp, gfp, - 0, NULL); + flags, NULL); if (desc->error) { if (desc->error == -EINVAL) desc->error = 0; @@ -1814,18 +1830,27 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ * We must evaluate after, since reads (unlike writes) * are called without i_mutex protection against truncate */ - nr = PAGE_CACHE_SIZE; i_size = i_size_read(inode); end_index = i_size >> PAGE_CACHE_SHIFT; + + nr = PAGE_CACHE_SIZE; +#ifdef CONFIG_TRANSPARENT_HUGEPAGE_PAGECACHE + if (page && PageTransHugeCache(page)) { + index &= ~HPAGE_CACHE_INDEX_MASK; + end_index &= ~HPAGE_CACHE_INDEX_MASK; + nr = PAGE_CACHE_SIZE << compound_order(page); + } +#endif + if (index == end_index) { - nr = i_size & ~PAGE_CACHE_MASK; - if (nr <= offset) { + nr = ((i_size - 1) & ~page_cache_to_mask(page)) + 1; + if (nr <= pos_to_off(page, *ppos)) { if (page) page_cache_release(page); break; } } - nr -= offset; + nr = nr - pos_to_off(page, *ppos); if (page) { /* @@ -1838,7 +1863,7 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ /* * Mark the page accessed if we read the beginning. */ - if (!offset) + if (!pos_to_off(page, *ppos)) mark_page_accessed(page); } else { page = ZERO_PAGE(0); @@ -1855,10 +1880,9 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ * "pos" here (the actor routine has to update the user buffer * pointers and the remaining count). */ - ret = actor(desc, page, offset, nr); - offset += ret; - index += offset >> PAGE_CACHE_SHIFT; - offset &= ~PAGE_CACHE_MASK; + ret = actor(desc, page, pos_to_off(page, *ppos), nr); + *ppos += ret; + index = *ppos >> PAGE_CACHE_SHIFT; page_cache_release(page); if (ret != nr || !desc->count) @@ -1867,7 +1891,7 @@ static void do_shmem_file_read(struct file *filp, loff_t *ppos, read_descriptor_ cond_resched(); } - *ppos = ((loff_t) index << PAGE_CACHE_SHIFT) + offset; + i_split_up_read(inode); file_accessed(filp); } -- 1.8.4 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
